Allen, CR, Fu, Y-C, Cazas-Moreno, V, Valliant, MW, Gdovin, JR, Williams, CC, and Garner, JC. Effects of jaw clenching and jaw alignment mouthpiece use on force production during vertical jump and isometric clean pull. J Strength Cond Res 32(1): 237-243, 2018-This study examined the effects of jaw clenching, a self-adapted, jaw-repositioning mouthpiece on force production during maximum countermovement vertical jump and maximum isometric midthigh clean pull assessments in an attempt to determine any ergogenic effect attributable to clenching, jaw-repositioning mouthpiece use, or the combination of both. Thirty-six male subjects performed vertical jump and isometric clean pull assessments from a force platform under various mouthpiece and clench conditions. A 3 × 2 (mouthpiece × clench) repeated-measures analysis of variance was conducted to analyze each of the following force production variables for both assessments: peak force, normalized peak force, and rate of force development. In addition, jump height was analyzed for the vertical jump. Results revealed improvements in peak force (F1,35 = 15.84, p ≤ 0.001, (Equation is included in full-text article.)= 0.31), normalized peak force (F1,35 = 16.28, p ≤ 0.001, (Equation is included in full-text article.)= 0.32), and rate of force development (F1,35 = 12.89, p = 0.001, (Equation is included in full-text article.)= 0.27) during the isometric clean pull assessment when participants maximally clenched their jaw, regardless of mouthpiece condition. There were no statistically significant differences in jump height, peak force, normalized peak force, or rate of force development during the vertical jump for any treatment condition. This study supports previous research demonstrating that the implementation of remote voluntary contractions such as jaw clenching can lead to concurrent activation potentiation and a resulting ergogenic effect during activities involving and requiring high-force production.

The purpose of this study was to investigate the effects of different warm-up (WU) devices on bat swing parameters including maximal resultant velocity (MRV), resultant velocity at ball contact (RVBC), time difference between MRV and RVBC, bat angle at MRV, bat angle at RVBC, and perceptual differences (PD) of each WU implement utilized by National Collegiate Athletic Association (NCAA) Division-I baseball players. Fifteen varsity baseball players completed one experimental session during fall training. Retro-reflective markers were placed on the bat and tee to measure basic bat kinematics during the swing. Participants completed a general calisthenics WU before being counter-balanced into one of four WU conditions: standard bat (SB) (33in/30oz), fungo (FG) (10.6oz), weighted gloves with SB (WG) (55.6oz) and donut with SB (DN) (55.6oz). Each participant was asked to perform their normal on deck routine over a two-minute period, finishing with 5 practice swings with the designated condition. After completion of the WU, a one-minute rest period (simulating normal game conditions) was given to allow each participant to get set to perform five maximal swings with a SB. Five, 1x4 (group x condition) repeated measures analysis of variance examined the aforementioned variables. There were no significant differences in MRV, RVBC, time difference between MRV and RVBC, and bat angle at MRV and RVBC between all WU conditions. If presented with the current options, athletes should choose the WU implement with which they are most comfortable using prior to an at bat situatiossn.

Background: Recreational athletes can select their desired footwear based on personal preferences of shoe properties such as comfort and weight. Commonly worn running shoes and cleated footwear with similar stud geometry and distribution are worn when performing sport-specific tasks such as a side-step cutting maneuver (SCM) in soccer and American football (hereafter, referred to as football). The effects of such footwear on injury mechanics have been documented with less being known regarding their effect on performance. Objective: The purpose of this study was to examine performance differences including peak ground reaction forces (pGRF), time-to-peak ground reaction forces (tpGRF) and the rate of force development (RFD) between football cleats (FB), soccer cleats (SOC), and traditional running sneakers (RUN) during the braking and propulsive phases of a SCM. Methodology: Eleven recreationally active males who participated in football and/or soccer-related activities at the time of testing completed the study. A 1 x 3 [1 Condition (SCM) x 3 Footwear (RUN, FB, SOC)] repeated measures ANOVA was utilized to analyze the aforementioned variables. Results: There were no significant differences (p > 0.05) between footwear conditions when comparing pGRF, tpGRF, or RFD in either the braking or propulsive phases. Conclusion: The results suggest that the studded and non-studded footwear allowed athletes to generate similar forces over a given time frame when performing a SCM.

No abstract

Purpose: The purpose of this study was to investigate the effects of general and specific warm-up protocols on rate of force development (RFD), relative RFD (rRFD), ground reaction force (GRF) and relative ground reaction force (rGRF) during an isometric mid-thigh pull (IMTP), after WBV exposure. Methods: Fifteen healthy recreationally trained males (age: 24.1 ± 2.3 yrs, height: 72.9 ± 7.8 cm; mass: 86.9 ± 8.3) completed five protocols: baseline, isometric vibration (iVib), isometric no vibration (iNV), dynamic vibration (dVib) and dynamic no vibration (dNV). The baseline was completed without any warm-up prior to the IMTP. The intervention protocols had the same prescription of 4 sets of 30-second bouts of quarter squats (dynamic [DQS] and isometric [IQS]) on the WBV platform with or without vibration. Following a one-minute rest period after each protocol, participants completed three maximal IMTPs. Results: Repeated measures ANOVA with a Bonferroni post hoc demonstrated that RFD in dNV (7657.8 ± 2292.5 N/s) was significantly greater than iVib (7156.4 ± 2170.0 N/s). However, the other experimental trials for RFD demonstrated no significant differences (p>0.05). There were also no significant differences for rRFD, GRF or rGRF between protocols. Conclusion: These results demonstrate that a dynamic warm-up without WBV elicits greater RFD than an isometric warm-up with WBV prior to a maximal isometric exercise. Further research needs to be investigated utilizing dynamic and isometric warm-ups in conjunction with WBV and power output.